Probing Effect of External UV Radiation on Young Stellar and Substellar Mass Objects: Is Orion a Special Place for Observing External Photoevaporation of Disks?

Does star and planet formation environment matter for their circumstellar disk evolution and their properties? What are the observational signatures and theoretical implication? UV radiation from massive stars may affect the disk properties including disk mass, disk size, accretion rate, and disk lifetime. The final mass of the young objects may be affected due to early loss of circumstellar materials.  The evidence of short-lived radioactive nuclides found in meteorites suggest that the planet forming solar system disk has been affected by massive stars and their death. These massive stars not only influence their neighboring stars via their dying processes, but while they are in main sequence via UV radiation and winds. We have been conducting systematic survey of the Orion star forming region where we have direct evidence of interplay between massive stars and young objects in their vicinity: photoevaporating protostellar disks (proplyds) evaporating away from massive stars. We have extensively studied the Orion star forming region including Orion Nebula Cluster (ONC), its sibling NGC 1977, NGC 1980, and Lynds 1641. Most of the proplyds have been found in Orion, while only handful of such objects have beeb found outside the Orion region around early to mid O stars. A B1V star, 42 Ori, in NGC 1977 is so far the lowest mass objects with multiple proplyds around it. We present our multi-wavelength observational and modeling results on proplyds around 42 Ori, candidate free-floating planetary mass proplyds in ONC and NGC 1977, and discuss the impact of external UV radiation environment on young stellar and substellar object formation.